Method of etching polysilicon using a thin oxide mask formed on the polysilicon while doping

Abstract

A polysilicon layer is deposited on a gate insulating film covering the surface of a semiconductor substrate, and thereafter the polysilicon layer is subjected to an impurity doping process in an oxidization atmosphere with heating, to reduce the resistance of the polysilicon layer, and to oxidize the surface of the polysilicon layer and form a silicon oxide film. The silicon oxide film is selectively etched to leave an etching mask. Thereafter, the polysilicon layer is selectively etched to leave an electrode layer or wiring layer by using etching gas not containing carbon and fluorine and using the etching mask. It is possible to obtain a high etching selection ratio with simple processes.

I claim: 
     
       1. A method of manufacturing a semiconductor device comprising the steps of: (a) forming a polysilicon layer on an insulative surface of a substrate;   (b) doping an impurity into said polysilicon layer in an oxidization atmosphere with heating, to reduce a resistance of said polysilicon layer and to oxidize a surface of said polysilicon layer and form a particle-less silicon oxide film thereon; and   (c) selectively etching said silicon oxide film to form an etching mask consisting solely of a remaining silicon oxide film formed in said step (b), and selectively etching said polysilicon layer through said etching mask to leave an electrode layer or wiring layer by using a carbon-free and fluorine-free etching gas.   
     
     
       2. A method according to claim 1, wherein said substrate is a silicon substrate having a silicon oxide layer on the surface of said substrate. 
     
     
       3. A method according to claim 1, wherein said step of forming said etching mask includes forming a resist pattern on said silicon oxide film, selectively etching said silicon oxide film by using said resist pattern as an etching mask, and removing said remaining resist pattern. 
     
     
       4. A method of manufacturing a semiconductor device comprising the steps of: (a) providing a substrate;   (b) forming a polysilicon layer on the substrate;   (c) doping an impurity into the polysilicon layer;   (d) concurrently with the step (c), forming a particle-less silicon oxide film on the polysilicon layer;   (e) forming a patterned mask consisting solely of the remaining silicon oxide film formed in step (d); and   (f) etching the polysilicon layer through the patterned mask of the silicon oxide film.   
     
     
       5. A method according to claim 4, wherein in the step (a), the substrate comprises a semiconductor material. 
     
     
       6. A method according to claim 5, wherein the substrate has an insulating layer formed thereon. 
     
     
       7. A method according to claim 4, wherein the polysilicon layer is formed using chemical vapor deposition (CVD). 
     
     
       8. A method according to claim 4, wherein the step (c), the impurity comprises a material selected from a group consisting of boron, phosphorus and arsenic. 
     
     
       9. A method according to claim 4, wherein the step (e) further comprises the steps of: forming a resist layer; and   (e-2) patterning the resist layer to form a resist mask.   
     
     
       10. A method according to claim 9, wherein the step (e) further comprises the steps of: (e-3) selectively etching the silicon oxide film using the resist mask; and   (e-4) removing the resist mask.   
     
     
       11. A method according to claim 10, wherein the patterned resist mask is removed in step (e-4) through an ashing process using H 2  SO 4  or H 2  O 2 . 
     
     
       12. A method according to claim 4, wherein in the step (f), the polysilicon layer is etched using a material selected from the group HBr, Cl 2 , HBr+O 2 , HBr+Cl 2 , and Cl 2  +O 2  +N 2 . 
     
     
       13. A method of manufacturing a semiconductor device comprising the steps of: (a) forming a polysilicon layer on a surface of a substrate;   (b) doping an impurity into said polysilicon layer in an oxidization atmosphere with heating so that a surface of said polysilicon layer is oxidized to form a silicon oxide film; and   (c) selectively etching said silicon oxide film to form a silicon oxide etching mask consisting solely of the remaining silicon oxide film formed in step (b) and selectively etching said polysilicon layer through said silicon oxide etching mask using a carbon-free and fluorine-free etching gas to leave an electrode layer or wiring layer.   
     
     
       14. A method according to claim 13, wherein in the step (c), the polysilicon layer is etched using a material selected from the group HBr, Cl 2 , HBr+O 2 , HBr+Cl 2 , and Cl 2  +O 2  +N. 
     
     
       15. A method according to claim 13, wherein the substrate comprises a semiconductor material. 
     
     
       16. A method according to claim 13, wherein the substrate has an insulating layer formed thereon.